Electrode for rectifiers and electrolytic condensers



Aug. 2 WET,

E. F. ANDREWS ELECTRODE FOR RECTIFIERS AND ELECTROLYTIC CONDENSERS fife/ways Filed Sept. 10, 1926 Patented Aim. 2, 1927,

PATENT OFFICE.

nnwarm 1'. nunnnws; or cnrcado. rumors, nssmuon' 'ro mnnEws-mmoun CORPORATION, OI CHICAGO, ILLINOIS,

A CORPORATION OF ILLINOIS.

ELECTRODE FOB IBEO'IIFIERS AND ELECTROLYTIC OONDENSERS.

' Application fled September 10, me. s m 10 134,851.

My invention relates to an electrode and to a substance for such electrode, which is adaptable for use with rectifiers and electrolytic condensers. I have shown it herein as applied in one instance to a battery charger or rectifier adapted to be used to charge, from a source of alternating current, storage batteries of the character used in connection with automobile starting and lighting "systems, and radio equipment.

It may be adapted however,

to any other purpose for which electrolytic rectifiers or condensers are required, such as the rectificationof alternating currents for power purposes, the supplying of pulsating cur rent from an alternating current source, which ulsating current can be smoothed into unitorm direct current by a filter system in which this alloy may also be used for the condensers if desired. My rectifying alloy is also especially adapted for use in conjunction with electro-chemical condensers described in my co-pending application. Ser. No. 128,959, filed August 13, 1926, to form a complete source of uniform direct current deriving its power from an alternating current supply and in which the rectifier and the electro-chemical condensers operate in the same electroiyte, as set iorth 1n the co-pendmg appiication oi Laurens Hammond, Ser. No. 111,959, filed May 27, 1926.

An object of the invention when used as arectifier is to provide an improved electrolytic rectifier which will operate in a solution of potassium hydroxide and in which both the filming and non-filming electrodes and also the electrolyte will be subject to a minimum of deterioration with age and use. A further object is to provide a rectifier having 'a high efiiciency. which will produce a relatively large direct current with a given consumption of alternating current and in which the heat produced by the rectifier per unit of direct current delivered is low. Another object is the provision of such a rectifier. the rectifying characteristics of which shall remain relatively constant during long periods of use or after standing idle for a considerable length of time. A further object is the provision of an electrode containing the elements, magnesium and aluminum, which shall be a relatively 'strong and durable structural material and at the same time possess the desired rectifying properties. A further object is the provision of an electrode. which when connected to the positive terminal of a direct current source and associated in an electrolyte with a suitable electrode connected to the negative terminal of said direct current source will form on its surface a non-conducting film which will almost entirel prevent the flow of direct current throng the electrolyte. A further object is to provide an electrode material which possesses any or all of the abovecharact'eristics in other alkaline solutions besides potassium hydroxide and also in certain nearly neutral or neutral solutions. And still a further object is to provide a rectifying elec trode composed of an alloy containing considerable quantities of aluminum and magnesium which shall have rectifying and blocking characteristics which are entirely different and altogether superior to either aluminum or magnesium itself. Another object of this invention is to provide a rectifier sufficiently permanent and sufficiently constant in its operating characteristics to adapt it for use to charge storage batteries by the so-called trickle charge method which require:- the practically continuous operation of the rectifier supplying a low rate of current to the battery throughout its life.

Other objects will appear from time to time in the course of the specification and claims.

I illustrate my invention more or'less diagrammatically 1n the accompanying drawings, wherein- Figure -1 is a side elevation withparts in section;

Figure 2 is a wiring diagram;

Figure 3 is a section through a variant form of my invention, illustrating its use as a condenser connected across a filter circuit;

Figure 4 is an enlarged section on the line 4-4 of Figure 3.

Like parts are indicated by like symbols throughout the specification and drawings.

Referring to the drawings, A indicates the charger container which may be of any suitable material, but which is herein shown as of a metal of the iron group. About the upper edge of the container are positioned inwardly projecting ledges A, upon which is positioned any suitable cover member A of any suitable insulating material, which may, for example, be of hard rubber, and is secured. in position, for exam la b the screws A. It may be provide wit the filler cap A, vented as at A.

The rectifying element of the charger shown in Figure 1 consists of one or more rectifying electrodes B, of a mixture or alloy of magnesium and aluminum the proportions of which will be later dlsoussed, and a non-rectifyin electrode B which ma be of nickel or 0 another metal of the iron group, or of any other metal suitable'for use in the articular electrolyte employed and which film.

As an'electrolyte, indicated as E, I may emplo any suitable liquid or solution su1table fbr use with electrodes of the above metals, but I prefer to employ an alkaline solution, and in articular, a solution of potassium hydroxi' e.

In the preferred form of my rectifier I employ two electrodes B, each secured to the cover plate A, for example by the non-conducting bushin C with the holding mm C. C is a metal p ate en aging the upper end B of the electrode. 5 are securing screws one of which\may serve as a bindin post, when employed in connection with t e nut C. The purpose of these bushings is to prevent contact between electrode and electrolyte at the surface of the electrolyte, as cr stalline. compounds are here formed. T is structure is not essential, and, if found desirable, the electrodes may be secured to the cover without the bushings. Also a layer of mineral oil may be emplo ed,if desired,-

on top of the solution, to ta e the place of the bushings, or both may be omitted Between the two magnesium aluminum allo electrodes I position a single non-rectifying electrode B, which in the preferred form consists of a plate of nickel or nickelplated iron, or of any metal or metals of the iron group. As an example of fastening means I illustrate the plate as formed at its upper edge with a flange D, secured to the cover plate by means 0 the screws D.

H indicates a supplemental housing, secured to the main housing A, and preferably positioned beneath it. It may be provided with any suitable switch mechanism H and a transformer H, the details of which form no art of the resent invention. Referrin to igure 2, a is the prima coil of t e transformer and H the secon ary coil, and H H the two leaves of the double switch H. H indicates a wall plug from which one conductor H extends to the primary coil H and another conductor H to the switch leaf H, H connects the v 0 posite end of the coilH with the contact which cooperates with the switch leaf H. From one end of the secondary coil H oes not form a non-conducting a conductor I extends to one of the rectifying electrodes B. From the opposite end of the secondary coil the conductor I extends to the other electrode B. Intermediate the conductor I extends the secondary coil H to the contact member 1 adapted to cooperate with the switch leaf H. From the non-rectifying electrode. B, intermediate the rectifying electrodes, extends the conductor 1", the negative terminal of the device, and from the switch H extends the conductor 1 the positive terminal of the device, to which ma be secured the usual clips I I as shown in igure 1.

In use, the plug H is plug ed into the electric li ht socket, the clips I I' are secured to t e terminals of the battery to be charged, or the circuit to be supplied, and

the switch H is actuated to move the switch leaves H H against the contacts H I respectively.

Figure 3 indicates a condenser including a metal container K, which may for example be of nickel plated iron, having a pluralit of internal transverse partitions K whic should be welded to the container and which may, if desired, be vented as at K, to permit the maintenance of the same liquid level in all compartments. K indicates the electrolyte in the various compartments.

is a cover of insulating material, to which are secured a plurality of electrodes L4, of the magnesium and aluminum alloy elsewhere herein discussed, in the form of plates. The plates may be supported by means of the members L and the screws or bolts L'. The plates may further be connected by means of the welded ieces or low resistance conductors L, wel ed to each plate. L indicates supporting or spacing locks of any suitable insulating material which ma be employed to support or to space the bottoms of the plates L.

M, M indicate the primary and secondary coils of a transformer connected with any suitable source of alternating current. M is'a conductor extendin to one of the bolts L which serves as a binding post for i the entire series of'plates L. M is a conductor extendin from the transformer to the container andthus to the partitions K 'which are welded to it. 'M indicates a choke coil between the transformer and the positive terminal and M indicates a conductor extending from the container K to the negatie terminal. It will be realized that whereas I have described and shown a practical and opera- "tive device and method, nevertheless many changes might be made in the size, shape, number and disposition of parts without departing from the spirit of my invention, and I therefore wish m drawings and description to be taken as in a broad sense illustrative and diagrammatic rather than as limitin me to my specific showing herein made. The use and operation of my invention are as follows:

Referring first to'the employment of my electrode in connection with a rectifier or trolytes, is practical and operable as a'rectifier, and is not attacked to an appreciable extent by these electrolytes. However lt'ls a rare and expensive metal, difficult to obtain and hard to handle. Beside which it uickly disintegrates in for example an alkaline electrolyte of sodium or potassium hydroxide.

Aluminum rectifies satisfactorily in some solutions, but under long continued use the characteristics of the rectifier change, owing to a number of causes, all of which tend to reduce the amount of current which Wlll .pass through such a rectifier. When an aluminum electrode stands idle, a non-conductive coating is formed of'such a nature and to such a depth as to necessitate the removal and cleaning as'a condition of further continued use. I Furthermore, aluminum rectifiers do not maintain constant cur rent characteristics. Also aluminum is violently attacked by electrolytes consisting of .sodium or potassium hydroxide, and rectifies only slightly in these electrolytes.

The use of a magnesium electrode in'a variety of solutions is disclosed and claimed in the co-pending application Ser. No. 111,959, filed by Laurens Hammond on May 27, 1926. Whatever may be the advantages of a magnesium electrode, such an electrode wastes in the course of its use and deposits a voluminous precipitate which necessitates a large container to receive it. The life of the rectifier is necessarily limited to the-life of the electrode, and the size of the electrode must be increased.

In order to construct a complete device for producing a uniform direct current from alternating current, such as described in the co-pending application of Mr. Laurens Hammond, Serial No. 111,959, filed May 27, 1926, utilizing the electro-chemical condenser described in my co-pending application above referred to, it is desirable to have a rectifier which will employ a solution of potassium hydroxide or sodium hydroxide as the electrolyte, particularly potassium hydroxide,

as this seems to be the best electrolyte for the above mentioned electro-chemical condenser. This also has the advantage of having'a very high conductivity. Whereas the magnesium rectifier will not operate in potassium hydroxide, this electrolyte is extremely well adapted for use with a rectify.- ing electrode composed of an alloy containing considerable quantities of alumnium and magnesium, or consisting entirely of these two substances, as long as the percentage of aluminum is greater than fifteen percent. Although a certain degrees of rectification can be had with less than fifteen per cent aluminum, the rectify' n action is relatively unstable in potassium hydroxide. An

alloy consisting of about e ual parts of each of the above mentioned su stances seems to be fully as good as any other from the point of view of its rectifying qualities alone. The essential difference of the rectification process produced by the addition of aluminum to magnesium is illustrated by the fact that if a clean alloy containing ten per cent of aluminum, the balance magnesium, is placed in an electrolyte of potassium carbonate, in which pure magnesium rectifiesthe best, it will not rectify at all. With high percentages of aluminum the alloy will rectify in carbonates. The efficiency of my alloy rectifier is very considerably greater than magnesium in carbonates, and 1ts tendency to heat up is correspondingly less. The throwing down of a heavy precipitate from the surface of the rectifying electrode together with its erosion, so characteristic of the magnesium rectifier, is almost totally absent when fifty per cent of aluminum is employed and is extremely slight-with thirty-three per cent of aluminum.

The proportions of aluminum and magnesium employed in my rectifying electrode can be established in 'a general way by the following considerations: If magnesium is the principal constituent, then aluminum must be present in sufficient quantities as to have a substantial effect on the rectifying characteristics. \Vith potassium hydroxide as an electrolyte consistent, continuous, rectification cannot be had with much less than fifteen per cent of aluminum. If aluminum is the principal constituent and the electrolyte is potassium hydroxide enough magnesium must be added to prevent the electrolyte from dissolving the electrode, as pure aluminum is attacked very rapidly by potassium hydroxide and most other alkalis. 33 1/3 per cent of magnesium is sufiicient for this purpose, in fact a smaller amount may The mechanical haracteristics of aluminum magnesium alloys are however an important factor in deciding upon the proportions to be used in the manufacture of practical electrodes. Aluminum alloys containing more than per centof have a very low ductility and magnesium alloyshaving above 15 per cent of aluminum also lack ductility. It appears necessary ood rectifier but crumbles easily and is disintegrated to some extent by the rectifying action. However an alloy consisting o 331/3 per cent aluminum and 662/3 per tical electrodes,- although it is quite The above discussion re-.

cent magnesium or thereaboutshas very good rectifying properties'in potassium hydroxide and is alsq amply strong for making racard and crystalline. lates, as to the specific proportions inentioned, primarily to the' use of myelectrodein an electrolyte consisting of solutionsof' potassium or sodium hydroxide. It. will be understood, however, that I do not limit 111 self to the .use of such solutionsand that t e proportions of the magnesium aluminum alloy may var widely, articularly when the alloy is emp oyed wit other 'elec'trol tes. Itwill be understood therefore that do not wish to limit myself-to the specific proportions or ranges above referred to, or to any specific proportion or range.

The mechanical properties of the alloy can also be to some extent'controlled bythe addition of other substances or metals which do not directly affect the rectifying char- I do not wish to-be limited to any specific proportion of cadmium, since the proportion may be varied to suit the particular conditions or desired consistenc I have found by experiment that an alloy consisting of 335/100 parts of aluminum, 3 35/100 parts of magnesium and one art of cadmium will produce an electrode w ich is very satisfac-' tory as far as its rectifying qualities are concerned but which has the objection of-being somewhat too brittle. When this electrode is used in potassium hydroxide with the nickel non-rectifyin electrode the solution remains almost per ectly clear and there is practically no precipitate. This" brittleness can be overcome by the addition of larger percentages of cadmium with the aluminum and magnesium content remaining equal. I do not wish however to be limited to any specific proportions of these three metals as desirable results can be obtained through a wide range of proportions.

rectification around points that lack homogeneity.

As a non-rectifying electrode I may emplog' a considerable range of metals, but I n that when a nickel late or member is used in a potassium hy roxide electrolyte, a rectifier is formed which is very stable in its rectifying characteristics, and which appearsto be unusually permanent, the rectifymg electrode bein attacked only to a very small extent, and t e non rectifyling electrode scarcely ;at all. .In general t e aluminum magnesium alloy electrode has the advantage that its rectifying characteristics are constant and do not change with age. An important advantage of the use of my electrode with the otassium hydroxide solution comes from t e fact that such solution is of low resistance or high conductivity.

The aluminum. magnesium alloy when used as the ositive electrode in an electrolytic cell will block a direct current almost completely. It may therefore unlike ure magnesium be employed as an electro ytic condenser. This quality also serves to revent the dischar e of a storage battery w 'ch is being charge the rectifier 1f the alternating current suply to the rectifier is interrupted. I ma owever, if it is desired to prevent absolute y by such a rectifier through all leakage from the storage battery employ the double switch structure and circuit described herein and shown in Figure 2, although this might not ordinarily be necessary.

I claim:

1. An electrode for an electrolytic-apparatus, which consists of an alloy of magnesium, aluminum and cadmium.

2. Anelectrode for an electrolytic apparatus, which consistsof an allo of magnesium, aluminum,-and additiona consistency controllin material.

3. An e ectrode for an electrolytic apparatus, which consists of an alloy includm magnesium, aluminum and cadmium in e fective proportions. p

4. An electrode for an electrolytic apparatus, which consists 'of an alloy having more than twenty-three per cent of magnesium and less than sevent -seven per cent of aluminum, associated wit an electrode of a metal of the iron group, in an electrolyte of potassium hydroxide.

5. An electrode for electrolytic rectifiers and condensers which includes an alloy having more than twenty-three per cent of magnesium and less than sevent -seven er cent of aluminum, associated with an e ectrode III of a metal of the iron group, in an electrolyte containing a hydroxide of an alkali metal in effective proportion.

6. In an electrode for electrolytic rectifiers and condensers which includes an alloy having more than twenty-three per cent of magnesium and less than seventy-seven per cent of aluminum. associated with an electrode including in effective proportion a metal of the iron group. in an electrolyte containing a hydroxide of an alkali metal in eltective proportion.

7. An electrode for electrolytic rectifiers and condensers, which includes magnesium and aluminum in efi ective proportions, said electrode containing less than thirty-threg and one-third per cent of magnesium andmore than twenty-three per cent, in an electrolyte'containing a hydroxide of an alkali metal in effective proportion..

8. An electrode for electrolytic rectifiers and condensers, comprising a magnesium aluminum alloy containing more than twenty-three per cent of magnesium, in an electrolyte containing a hydroxide of an alkali metal in etlective proportion.

9. An electrode for electrolytic rectifiers and condensers, which includes magnesium and aluminum in effective proportions, said electrode containingless than thirty-three and one-third per cent of magnesium and more than twenty-three per cent, associated with an electrode including in effective proportion a metal of the iron group, in an electrolyte containing a hydroxide of an alkali metal in effective proportion.

10. An electrode for electrolytic rectifiers and condensers, comprising a magnesium aluminum alloy containing more than twenty-three per cent of magnesium, associated with an electrode including in eflective proportion a metal of the iron group, in an electrolyte containing a hydroxide of an alkali metal in efiective proportion.

11. An electrode for electrolytic rectifiers twenty-three per cent of magnesium, associated with a nickel electrode, in an alkali metal hydroxide electrolyte.

13. In an electrolytic film forming apparatus an electrode which consists of an alloy of aluminum and magnesium having not less than 23 percent of magnesium.

14. In an electrolytic film forming apparatus an electrode which consists of an alloy of magnesium and aluminum having not less than 23 percent "of magnesium, and an electrode of a metal of the iron group in an alkaline electrolyte.

15. In an electrolytic rectifier or condenser an electrode which consists of an alloy of magnesium and aluminum having not less than 23 percent of magnesium, an electrode including in effective proportion 21 metal of the iron group.

16. In an electrolytic rectifier or condenser a rectifying electrode which consists of an alloy of aluminum and magnesium having not less than 23 percent of mag- 'nesium.

17. In an electrolytic rectifier or con denser a rectifying electrode which consists of an alloy of aluminum and magnesium having not less than 23 percent of magnesium and a non-rectifying electrode containin; ametal *of the iron group.

Signed at Chicago, county of Cook and State of Illinois, this 26th day of August, 1926;

EDWARD F. ANDREWS. 

